The south wall just has a regular 3-prong plug outlet. It's not the wierd shaped plug. Are there any plug-in couplers that accommadate a regular 3-prong plug? My home is about 40 years old.
Just curious... Was there ever a room AC plugged in at the south wall? Do you use the "regular 3-prong plug outlet"? If not, check the voltage and wiring there. Have you lived in the house since it was new? Any modifications to the south wall? i.e. Can you vouch for the wiring over the history of the house? (I've seen some strange wiring arrangements by do-it-yourselfers.)
I grew up in a house that didn't have central air. My parents later installed a couple room AC units. While our units were 110V, I remember recommendations that they have a dedicated outlet. The 220V room units require wiring for 220V. Central air was added later.
Well, half of my homes outlets don't work because the interface is using one leg. Is this correct? Wouldn't a phase coupler do the job?...
That clearly points to the need for a coupler. Now you just need to figure out where to put it.
...I have no 220v outlets in my home.
No drier plug?
If the "220V to s wall" is not being used, you could have an electrician wire an approved coupler from that box. It might also be useful to have an electrician check your wiring.
I'd also recommend turning the breaker "OFF". If you're not using it would be safer that way. You also may discover that some "creative wiring" (to code or perhaps not) where the 220V has been split elsewhere in the house.